1. Technical Field
The present invention relates to a resonator element provided with step parts on the side surfaces of the vibrating arms, and a resonator, a physical quantity sensor, and electronic equipment including the resonator element.
2. Related Art
In related art, in a tuning fork resonator including a vibrating arm having excitation electrodes and a vibrating arm having detection electrodes, there is a form in which the sectional shapes of the vibrating arms are substantially rectangular shapes, electrodes are provided on front and rear surfaces and both side surfaces of the vibrating arms, flexural vibrations of the vibrating arms are generated, and a natural resonance frequency is oscillated.
Further, as another form, when the vibrating arm is in in-plane vibration by an excitation signal, if the shaft of the vibrating arm in the extending direction is rotated as a detection shaft, the vibrating arm is brought into out-of-plane vibration by Coriolis force. Since the amplitude of the out-of-plane vibration is proportional to the rotational speed of the tuning fork resonator, there is an angular velocity sensor (physical quantity sensor) that can detects it as an angular velocity.
The detection electrodes are divisionally provided on both side surfaces in the in-plane vibration direction of one vibration arm, and the opposed detection electrodes and the detection electrodes on the same side surfaces have different polarities (for example, see Patent Document 1 (JP-A-5-256723)).
Recently, electronic equipment has tended to be smaller and the smaller size of the tuning fork resonator element has been demanded. If the widths of the vibrating arms are made narrower as the resonator element is made smaller, the widths of the electrodes may not taken larger, and the electrode area decreases and the electric field applied to the vibrating arm thereby becomes weaker as it is nearer the center of the section of the vibrating arm.
There has been a problem of the resonator element that the vibration loss becomes greater due to the deterioration of the electric field efficiency.
Further, in the case where the resonator element is used as an angular velocity sensor, in Patent Document 1, the electric field is linear and electric charge is easier to be detected because the detection electrodes are opposed, however, it is necessary to divide the detection electrodes on both side surfaces of the vibrating arm. These detection electrodes are formed by means of sputtering or the like from a direction along the side surfaces, and it is difficult to form the electrodes divisionally in the side surface direction (the thickness direction of the resonator element).
Furthermore, since the distance between the opposed detection electrodes depends on the widths of the vibrating arms themselves, the distance between the electrodes may not simply be made smaller. The generated charge due to the vibration produced by Coriolis force is proportional to the capacitance between electrodes and the capacitance is inversely proportional to the distance between electrodes, and thus, there is a problem that, when the distance between electrodes is larger, the generated charge is smaller and the detection sensitivity is lower.